This invention relates to a video game peripheral device having a photosensitive element for sensing the relative position of the field of view of the device in relation to a video monitor screen, and in particular to such a device that is compatible with a personal computer based game platform.
Video games are extremely popular for many reasons attributable to the game being played, as well as the variety of different input devices available for use in controlling or playing the game. For example, input devices include joysticks, steering wheels, gas/brake pedal assemblies, and photosensitive light guns. Light guns are particularly popular for use with games where targets are presented on the screen and the player must shoot the target by pointing the gun at the target and pulling a trigger.
In the home-based video game market, there are two basic types of platforms in use; the dedicated console platform, and the personal computer platform. Dedicated consoles are self-contained microprocessor-based units that function to receive game modules such as ROM cartridges or CD-ROMs, execute the instructions on the game module, and present the game's images and sounds to the player(s) via a conventional television set (or optionally a self-contained display screen). Input devices such as the light gun are connected to the console to allow the player to control the operation of the game in conjunction with the images viewed and sounds heard via the television set.
Personal computer based video games take advantage of existing computers already in use by millions of people, by allowing a player to play a game by simply loading and executing a video game program. Usually, a joystick is connected to a game port located within the computer, which allows the player to control operation of the game since the game port is coupled to the CPU via the computer's various buses. If a joystick or game port is not available, the player may be able to control the game with the keyboard or mouse, but the ergonomics presented by these devices do not lend themselves to efficient playing or enjoyment of the game.
Although many games can be played on the personal computer platform without the joystick, it is not practical to play a shooting game unless a light gun is utilized. That is, the very nature of the shooting game requires the player to aim at the screen with a sight on the gun and pull a trigger at the desired time in hopes of "hitting" the target. There is no practical way of emulating this experience with a keyboard or mouse since they cannot be aligned visually with the screen targets, and they cannot provide the screen positional feedback data (to be described below) to the CPU that is necessary to control the game.
Light guns have been used with television sets connected to dedicated consoles for several years. The light gun relies on the physics of the television screen to detect the specific location at which the light gun is pointed at any particular time. As well known in the art, television screens utilize a scanning electron beam (or beams) that trace horizontally and vertically in a raster pattern to form the image that the viewer's eyes perceive. As an aid in generating the raster pattern, horizontal and vertical synchronization signals are generated by the control electronics that produce the video signal and then detected and used by the electronics associated with the television to properly reproduce the image across the screen.
Although the scanning of the beam across and down the screen is generally not perceivable to the human eye, it is possible for a photosensitive device to detect the existence of the beam at a particular position on the screen. This is the basis on which light guns operate with dedicated video game consoles in use today. Thus, the light gun has a photosensitive device located at the tip of the simulated gun, as well as an electronic switch that is actuatable by pulling a simulated trigger. When the photosensitive device is pointed at a target area on the screen, it will sense when the electron beam is scanned across the screen and send that information (optionally in conjunction with a trigger press) to an input port on the dedicated game console. Since the CPU in the game console generated the images to be displayed on the screen, and in particular since it generated the horizontal and vertical synchronization signals, it can determine the relative position on the screen at which the light gun was aimed by calculating the phase difference between the start of the raster pattern and the time the electron beam was sensed by the photosensitive device.
Notwithstanding their popularity, light guns have heretofore not been able to be used with video games running on personal computers because of the certain differences that exist between the dedicated game console and the personal computer, which make the conventional light gun impossible to use. In a personal computer, the CPU provides digital image data in the form of frames or bit maps to a video adapter board (e.g., a VGA or SVGA board). The video adapter board then generates the appropriate red, green and blue analog signals that are output to the monitor (so-called RGB signals). Importantly, the video board also generates the synchronization timing signals (vertical and horizontal synch) that are also sent to the monitor to control the scanning raster. Since the CPU did not generate the synch signals, it cannot calculate the relative position on the screen at which the light gun was aimed. That is, the CPU cannot calculate the phase difference between the start of the raster pattern and the time the electron beam was sensed by the photosensitive device since it does not know when the synch signals were generated. Thus, the personal computer platform is disadvantaged from the dedicated game console since a conventional light gun cannot be used in game play.
One prior art system (by A-FOUR TECH CO., LTD.) attempts to overcome this disadvantage by providing an add-on board that must be inserted into an empty ISA slot on the motherboard. A ribbon cable is then connected from the add-on board to a VGA Feature Connector on the VGA card, and the light gun is plugged into the add-on board. This requires the user to open the computer, and install the add-on board and cable. This may not be practical since there may be no open board slots on the motherboard, the user may be unable to perform the technical operation of installing add-on boards, etc. In addition, the user cannot easily transfer the light gun to another computer without having to disassemble his computer, remove the add-on board, and install it on a companion's computer. This system is thus disadvantageous for most users.
It is therefore an object of the present invention to overcome the prior art and provide a light gun system that can be utilized with a conventional personal computer video game platform.
It is a further object of the invention to provide such a light gun system that will not require modification to the personal computer platform.
It is a still further object of the present invention to provide such a light gun system that can be easily installed without having to dismantle the personal computer to install additional circuitry.